As the fighting broke out, al-Sadr issued a statement calling for demonstrations across the country and threatened "civil disobedience" if attacks by US and Iraqi forces on members of his movement continued.

"We demand that religious and political leaders intervene to stop the attacks on poor people," a statement read by Hazam al-Aaraji, an al-Sadr representative, said.

"We call on all Iraqis to launch protests across all the provinces. If the government does not respect these demands, the second step will be general civil disobedience in Baghdad and the Iraqi provinces."

Falah Shenshal, an MP allied to al-Sadr, told Al Jazeera that al-Maliki was targeting political opponents.

"They say they target outlaw gangs but why do they start with the areas where the sons of the Sadr movement are located?"

"This is a political battle ... for the political interests of one party [al-Maliki's Dawa party] because the local elections are coming soon.

"They are using the law for their political interests. We will ask the parliament to drop confidence from the Maliki government."

Basra operation

The fighting in Basra, where al-Sadr's followers maintain a strong presence, began before dawn on Tuesday in what the Iraqi government called an operation to win control of the city from militias and criminal gangs.

Nuri al-Maliki, Iraq's prime minister, was in the oil hub city to personally oversee the operation involving thousands of Iraqi troops.

Ali al-Dabbagh, an Iraqi government spokesman, told Al Jazeera that the security forces were fighting against "those that are exploiting the name of the Mahdi, those that are exploiting the name of Muqtada al-Sadr".

"This ongoing operation in Basra appears to be security-related, while, in fact, it is a political one," he told Al Jazeera.

"The al-Sadr trend in Basra has frequently said that it supports the Iraqi government and the Iraqi forces in Basra.

"Al-Mahdi Army is not a military army, as some believe. It is a doctrinal army that serves the society. And that is why al-Mahdi Army has had a great role in supporting the Iraqi security forces in Basra."

Basra province was handed over to Iraqi control by British forces in mid-December and Tuesday's operation was seen as a test for the security forces.